Conductive property of nano silver ink on flexographic prints

This research is aimed to study the possibility of applying a flexographic printing with nano-silver ink for fabricating conductive lines on paper and film substrates. The rheological behavior of ink and the varying effects of anilox line screen on printing speeds and print quality were investigated. Printed layer thickness and its resistivity were analyzed. It was found that non linearlty of ink gave little effects on relationships between image parameters and printing conditions. It is because the viscosity of nano-silver ink is much lower than that of common water based flexographic ink. Press setting, packing material and rubber ink fountain roller should be in good conditions to protect printing problems such as ghosting and wave patterning. Results showed that anilox line screen did not relate well to print quality, while higher printing speed rather gave preferable printed results such as better resolution and low spreading, but non-homogeneity of solid area was still existed. The smallest text size which could be produced was 6 pt for positive font and 8 pt for negative font. Anilox line screen 600 lpi and printing speed 60 m/min was proposed as best condition in this study. Image of 0.1 mm finest line with about 10% width spreading and 5 µm thickness was achieved. An average sheet resistivity was at 1.26 ± 0.06 /cm2. This obtained value is a little larger than that of practical RFID devices.本研究旨在探究采用纳米银油墨进行柔版印刷（flexographic printing），以在纸张与薄膜基材上制备导电线的可行性。本研究考察了油墨的流变行为，以及网纹辊线屏（anilox line screen）对印刷速度与印刷质量的不同影响，并对印刷层厚度及其电阻率进行了分析。研究发现，油墨的非线性对图像参数与印刷条件之间的关联影响极小，这是由于纳米银油墨的黏度远低于常规水性柔版印刷油墨。需确保印刷机组设定、衬垫材料与橡胶墨斗辊处于良好状态，以避免鬼影（ghosting）与波纹图案（wave patterning）等印刷故障。结果表明，网纹辊线屏与印刷质量并无显著关联；而更高的印刷速度反而能获得更优的印刷效果，如更高的分辨率与更低的扩线率，但实地区域仍存在非均匀性问题。本次研究可制备的最小文字尺寸为：正体字6 pt，负体字8 pt。本研究推荐的最优工艺条件为：网纹辊线屏600 lpi，印刷速度60 m/min。最终可实现最细线条宽度为0.1 mm，线条扩宽率约10%，厚度为5 µm的印刷图案。试样的平均电阻率为1.26 ± 0.06 Ω/cm²，该测得值略高于实际射频识别（RFID）设备的电阻率。